diff --git a/tests/compile-fail/stacked_borrows/alias_through_mutation.rs b/tests/compile-fail/stacked_borrows/alias_through_mutation.rs
new file mode 100644
index 000000000000..9fa50da45bd0
--- /dev/null
+++ b/tests/compile-fail/stacked_borrows/alias_through_mutation.rs
@@ -0,0 +1,15 @@
+#![allow(unused_variables)]
+
+// This makes a ref that was passed to us via &mut alias with things it should not alias with
+fn retarget(x: &mut &u32, target: &mut u32) {
+    unsafe { *x = &mut *(target as *mut _); }
+}
+
+fn main() {
+    let target = &mut 42;
+    let mut target_alias = &42; // initial dummy value
+    retarget(&mut target_alias, target);
+    // now `target_alias` points to the same thing as `target`
+    *target = 13;
+    let _val = *target_alias; //~ ERROR should be frozen
+}
diff --git a/tests/compile-fail/validation_aliasing_mut1.rs b/tests/compile-fail/stacked_borrows/aliasing_mut1.rs
similarity index 100%
rename from tests/compile-fail/validation_aliasing_mut1.rs
rename to tests/compile-fail/stacked_borrows/aliasing_mut1.rs
diff --git a/tests/compile-fail/validation_aliasing_mut2.rs b/tests/compile-fail/stacked_borrows/aliasing_mut2.rs
similarity index 100%
rename from tests/compile-fail/validation_aliasing_mut2.rs
rename to tests/compile-fail/stacked_borrows/aliasing_mut2.rs
diff --git a/tests/compile-fail/validation_aliasing_mut3.rs b/tests/compile-fail/stacked_borrows/aliasing_mut3.rs
similarity index 100%
rename from tests/compile-fail/validation_aliasing_mut3.rs
rename to tests/compile-fail/stacked_borrows/aliasing_mut3.rs
diff --git a/tests/compile-fail/validation_aliasing_mut4.rs b/tests/compile-fail/stacked_borrows/aliasing_mut4.rs
similarity index 100%
rename from tests/compile-fail/validation_aliasing_mut4.rs
rename to tests/compile-fail/stacked_borrows/aliasing_mut4.rs
diff --git a/tests/compile-fail/validation_buggy_as_mut_slice.rs b/tests/compile-fail/stacked_borrows/buggy_as_mut_slice.rs
similarity index 52%
rename from tests/compile-fail/validation_buggy_as_mut_slice.rs
rename to tests/compile-fail/stacked_borrows/buggy_as_mut_slice.rs
index 282e536ce9b7..3345668cee00 100644
--- a/tests/compile-fail/validation_buggy_as_mut_slice.rs
+++ b/tests/compile-fail/stacked_borrows/buggy_as_mut_slice.rs
@@ -1,22 +1,17 @@
-// ignore-test validation_op is disabled
-
 #![allow(unused_variables)]
 
-// For some reason, the error location is different when using fullmir
-// error-pattern: in conflict with lock WriteLock
-
 mod safe {
     use std::slice::from_raw_parts_mut;
 
     pub fn as_mut_slice<T>(self_: &Vec<T>) -> &mut [T] {
         unsafe {
-            from_raw_parts_mut(self_.as_ptr() as *mut T, self_.len())
+            from_raw_parts_mut(self_.as_ptr() as *mut T, self_.len()) //~ ERROR shared borrow for mutation
         }
     }
 }
 
 fn main() {
     let v = vec![0,1,2];
-    let v1_ = safe::as_mut_slice(&v);
-    let v2_ = safe::as_mut_slice(&v);
+    let v1 = safe::as_mut_slice(&v);
+    let v2 = safe::as_mut_slice(&v);
 }
diff --git a/tests/compile-fail/validation_buggy_split_at_mut.rs b/tests/compile-fail/stacked_borrows/buggy_split_at_mut.rs
similarity index 79%
rename from tests/compile-fail/validation_buggy_split_at_mut.rs
rename to tests/compile-fail/stacked_borrows/buggy_split_at_mut.rs
index a750f1466f51..d7f4300f82c0 100644
--- a/tests/compile-fail/validation_buggy_split_at_mut.rs
+++ b/tests/compile-fail/stacked_borrows/buggy_split_at_mut.rs
@@ -1,5 +1,3 @@
-// ignore-test validation_op is disabled
-
 #![allow(unused_variables)]
 
 mod safe {
@@ -20,5 +18,7 @@ mod safe {
 
 fn main() {
     let mut array = [1,2,3,4];
-    let _x = safe::split_at_mut(&mut array, 0); //~ ERROR: in conflict with lock WriteLock
+    let (a, b) = safe::split_at_mut(&mut array, 0);
+    a[1] = 5; //~ ERROR does not exist on the stack
+    b[1] = 6;
 }
diff --git a/tests/compile-fail/stacked_borrows/illegal_write.rs b/tests/compile-fail/stacked_borrows/illegal_write.rs
new file mode 100644
index 000000000000..6a7ccc84012c
--- /dev/null
+++ b/tests/compile-fail/stacked_borrows/illegal_write.rs
@@ -0,0 +1,11 @@
+fn evil(x: &u32) {
+    let x : &mut u32 = unsafe { &mut *(x as *const _ as *mut _) };
+    *x = 42; // mutating shared ref without `UnsafeCell`
+}
+
+fn main() {
+    let target = 42;
+    let ref_ = &target;
+    evil(ref_); // invalidates shared ref
+    let _x = *ref_; //~ ERROR should be frozen
+}
diff --git a/tests/compile-fail/stacked_borrows/illegal_write2.rs b/tests/compile-fail/stacked_borrows/illegal_write2.rs
new file mode 100644
index 000000000000..1d61b1b98896
--- /dev/null
+++ b/tests/compile-fail/stacked_borrows/illegal_write2.rs
@@ -0,0 +1,10 @@
+#![allow(unused_variables)]
+
+fn main() {
+    let target = &mut 42;
+    let target2 = target as *mut _;
+    drop(&mut *target); // reborrow
+    // Now make sure our ref is still the only one
+    unsafe { *target2 = 13; } // invalidate our ref
+    let _val = *target; //~ ERROR does not exist on the stack
+}
diff --git a/tests/compile-fail/stacked_borrows/pointer_smuggling.rs b/tests/compile-fail/stacked_borrows/pointer_smuggling.rs
new file mode 100644
index 000000000000..3576aa52b753
--- /dev/null
+++ b/tests/compile-fail/stacked_borrows/pointer_smuggling.rs
@@ -0,0 +1,22 @@
+#![allow(unused_variables)]
+
+static mut PTR: *mut u8 = 0 as *mut _;
+
+fn fun1(x: &mut u8) {
+    unsafe {
+        PTR = x;
+    }
+}
+
+fn fun2() {
+    // Now we use a pointer we are not allowed to use
+    let _x = unsafe { *PTR };
+}
+
+fn main() {
+    let val = &mut 0; // FIXME: This should also work with a local variable, but currently it does not.
+    fun1(val);
+    *val = 2; // this invalidates any raw ptrs `fun1` might have created.
+    fun2(); // if they now use a raw ptr they break our reference
+    *val = 3; //~ ERROR does not exist on the stack
+}
diff --git a/tests/compile-fail/stacked_borrows/shared_confusion.rs b/tests/compile-fail/stacked_borrows/shared_confusion.rs
new file mode 100644
index 000000000000..584053f59323
--- /dev/null
+++ b/tests/compile-fail/stacked_borrows/shared_confusion.rs
@@ -0,0 +1,21 @@
+#![allow(unused_variables)]
+use std::cell::RefCell;
+
+fn test(r: &mut RefCell<i32>) {
+    let x = &*r; // not freezing because interior mutability
+    let mut x_ref = x.borrow_mut();
+    let x_inner : &mut i32 = &mut *x_ref; // Uniq reference
+    let x_evil = x_inner as *mut _;
+    {
+        let x_inner_shr = &*x_inner; // frozen
+        let y = &*r; // outer ref, not freezing
+        let x_inner_shr2 = &*x_inner; // freezing again
+    }
+    // Our old raw should be dead by now
+    unsafe { *x_evil = 0; } // this falls back to some Raw higher up the stack
+    *x_inner = 12; //~ ERROR does not exist on the stack
+}
+
+fn main() {
+    test(&mut RefCell::new(0));
+}
diff --git a/tests/compile-fail/validation_illegal_write.rs b/tests/compile-fail/validation_illegal_write.rs
deleted file mode 100644
index cb3e4b3c1a20..000000000000
--- a/tests/compile-fail/validation_illegal_write.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-// ignore-test validation_op is disabled
-
-#![allow(unused_variables)]
-
-mod safe {
-    pub(crate) fn safe(x: &u32) {
-        let x : &mut u32 = unsafe { &mut *(x as *const _ as *mut _) };
-        *x = 42; //~ ERROR: in conflict with lock ReadLock
-    }
-}
-
-fn main() {
-    let target = &mut 42;
-    let target_ref = &target;
-    // do a reborrow, but we keep the lock
-    safe::safe(&*target);
-}
diff --git a/tests/compile-fail/validation_lock_confusion.rs b/tests/compile-fail/validation_lock_confusion.rs
deleted file mode 100644
index 2a0857659622..000000000000
--- a/tests/compile-fail/validation_lock_confusion.rs
+++ /dev/null
@@ -1,26 +0,0 @@
-// ignore-test validation_op is disabled
-
-// Make sure validation can handle many overlapping shared borrows for different parts of a data structure
-#![allow(unused_variables)]
-use std::cell::RefCell;
-
-fn evil(x: *mut i32) {
-    unsafe { *x = 0; } //~ ERROR: in conflict with lock WriteLock
-}
-
-fn test(r: &mut RefCell<i32>) {
-    let x = &*r; // releasing write lock, first suspension recorded
-    let mut x_ref = x.borrow_mut();
-    let x_inner : &mut i32 = &mut *x_ref; // new inner write lock, with same lifetime as outer lock
-    {
-        let x_inner_shr = &*x_inner; // releasing inner write lock, recording suspension
-        let y = &*r; // second suspension for the outer write lock
-        let x_inner_shr2 = &*x_inner; // 2nd suspension for inner write lock
-    }
-    // If the two locks are mixed up, here we should have a write lock, but we do not.
-    evil(x_inner as *mut _);
-}
-
-fn main() {
-    test(&mut RefCell::new(0));
-}
diff --git a/tests/compile-fail/validation_pointer_smuggling.rs b/tests/compile-fail/validation_pointer_smuggling.rs
deleted file mode 100644
index 14d624286038..000000000000
--- a/tests/compile-fail/validation_pointer_smuggling.rs
+++ /dev/null
@@ -1,22 +0,0 @@
-// ignore-test validation_op is disabled
-
-#![allow(unused_variables)]
-
-static mut PTR: *mut u8 = 0 as *mut _;
-
-fn fun1(x: &mut u8) {
-    unsafe {
-        PTR = x;
-    }
-}
-
-fn fun2() {
-    // Now we use a pointer we are not allowed to use
-    let _x = unsafe { *PTR }; //~ ERROR: in conflict with lock WriteLock
-}
-
-fn main() {
-    let mut val = 0;
-    fun1(&mut val);
-    fun2();
-}
diff --git a/tests/compile-fail/validation_recover1.rs b/tests/compile-fail/validation_recover1.rs
deleted file mode 100644
index 9061070ef67e..000000000000
--- a/tests/compile-fail/validation_recover1.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-// ignore-test validation_op is disabled
-
-#![allow(unused_variables)]
-
-#[repr(u32)]
-enum Bool { True }
-
-mod safe {
-    pub(crate) fn safe(x: &mut super::Bool) {
-        let x = x as *mut _ as *mut u32;
-        unsafe { *x = 44; } // out-of-bounds enum discriminant
-    }
-}
-
-fn main() {
-    let mut x = Bool::True;
-    safe::safe(&mut x); //~ ERROR: invalid enum discriminant
-}
diff --git a/tests/compile-fail/validation_recover2.rs b/tests/compile-fail/validation_recover2.rs
deleted file mode 100644
index 7a4a417ab1db..000000000000
--- a/tests/compile-fail/validation_recover2.rs
+++ /dev/null
@@ -1,16 +0,0 @@
-// ignore-test validation_op is disabled
-
-#![allow(unused_variables)]
-
-mod safe {
-    // This makes a ref that was passed to us via &mut alias with things it should not alias with
-    pub(crate) fn safe(x: &mut &u32, target: &mut u32) {
-        unsafe { *x = &mut *(target as *mut _); }
-    }
-}
-
-fn main() {
-    let target = &mut 42;
-    let mut target_alias = &42; // initial dummy value
-    safe::safe(&mut target_alias, target); //~ ERROR: in conflict with lock ReadLock
-}
diff --git a/tests/compile-fail/validation_recover3.rs b/tests/compile-fail/validation_recover3.rs
deleted file mode 100644
index 5cfc8aaa66b5..000000000000
--- a/tests/compile-fail/validation_recover3.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-// ignore-test validation_op is disabled
-
-#![allow(unused_variables)]
-
-mod safe {
-    pub(crate) fn safe(x: *mut u32) {
-        unsafe { *x = 42; } //~ ERROR: in conflict with lock WriteLock
-    }
-}
-
-fn main() {
-    let target = &mut 42u32;
-    let target2 = target as *mut _;
-    drop(&mut *target); // reborrow
-    // Now make sure we still got the lock
-    safe::safe(target2);
-}
diff --git a/tests/compile-fail/validation_undef.rs b/tests/compile-fail/validation_undef.rs
deleted file mode 100644
index 939e93a264e8..000000000000
--- a/tests/compile-fail/validation_undef.rs
+++ /dev/null
@@ -1,16 +0,0 @@
-// ignore-test validation_op is disabled
-
-#![allow(unused_variables)]
-// error-pattern: attempted to read undefined bytes
-
-mod safe {
-    use std::mem;
-
-    pub(crate) fn make_float() -> f32 {
-        unsafe { mem::uninitialized() }
-    }
-}
-
-fn main() {
-    let _x = safe::make_float();
-}
diff --git a/tests/compile-fail/validation_cast_fn_ptr1.rs b/tests/compile-fail/validity/cast_fn_ptr1.rs
similarity index 100%
rename from tests/compile-fail/validation_cast_fn_ptr1.rs
rename to tests/compile-fail/validity/cast_fn_ptr1.rs
diff --git a/tests/compile-fail/validation_cast_fn_ptr2.rs b/tests/compile-fail/validity/cast_fn_ptr2.rs
similarity index 100%
rename from tests/compile-fail/validation_cast_fn_ptr2.rs
rename to tests/compile-fail/validity/cast_fn_ptr2.rs
diff --git a/tests/compile-fail/invalid_bool.rs b/tests/compile-fail/validity/invalid_bool.rs
similarity index 100%
rename from tests/compile-fail/invalid_bool.rs
rename to tests/compile-fail/validity/invalid_bool.rs
diff --git a/tests/compile-fail/invalid_char.rs b/tests/compile-fail/validity/invalid_char.rs
similarity index 100%
rename from tests/compile-fail/invalid_char.rs
rename to tests/compile-fail/validity/invalid_char.rs
diff --git a/tests/compile-fail/invalid_enum_discriminant.rs b/tests/compile-fail/validity/invalid_enum_discriminant.rs
similarity index 100%
rename from tests/compile-fail/invalid_enum_discriminant.rs
rename to tests/compile-fail/validity/invalid_enum_discriminant.rs
diff --git a/tests/compile-fail/validity/transmute_through_ptr.rs b/tests/compile-fail/validity/transmute_through_ptr.rs
new file mode 100644
index 000000000000..0a4c64bb9bb1
--- /dev/null
+++ b/tests/compile-fail/validity/transmute_through_ptr.rs
@@ -0,0 +1,16 @@
+#![allow(unused_variables)]
+
+#[repr(u32)]
+enum Bool { True }
+
+fn evil(x: &mut Bool) {
+    let x = x as *mut _ as *mut u32;
+    unsafe { *x = 44; } // out-of-bounds enum discriminant
+}
+
+fn main() {
+    let mut x = Bool::True;
+    evil(&mut x);
+    let _y = x; // reading this ought to be enough to trigger validation
+    //~^ ERROR invalid enum discriminant 44
+}
diff --git a/tests/compile-fail/validity/undef.rs b/tests/compile-fail/validity/undef.rs
new file mode 100644
index 000000000000..58d3926dadaf
--- /dev/null
+++ b/tests/compile-fail/validity/undef.rs
@@ -0,0 +1,12 @@
+#![allow(unused_variables)]
+// error-pattern: encountered undefined data in pointer
+
+use std::mem;
+
+fn make_raw() -> *const f32 {
+    unsafe { mem::uninitialized() }
+}
+
+fn main() {
+    let _x = make_raw();
+}
diff --git a/tests/compiletest.rs b/tests/compiletest.rs
index b240fb31d222..7bec3fa8de2c 100644
--- a/tests/compiletest.rs
+++ b/tests/compiletest.rs
@@ -63,6 +63,7 @@ fn compile_fail(sysroot: &Path, path: &str, target: &str, host: &str, need_fullm
     flags.push(format!("--sysroot {}", sysroot.display()));
     flags.push("-Dwarnings -Dunused".to_owned()); // overwrite the -Aunused in compiletest-rs
     config.src_base = PathBuf::from(path.to_string());
+    flags.push("-Zmir-opt-level=0".to_owned()); // optimization circumvents some stacked borrow checks
     flags.push("-Zmir-emit-validate=1".to_owned());
     config.target_rustcflags = Some(flags.join(" "));
     config.target = target.to_owned();